EGR is a technique used in internal combustion engines to mitigate emissions of NOx. An internal combustion engine may suffer an efficiency penalty due to the work required to drive the recirculated exhaust gas directly from an engine's exhaust manifold to an engine's intake system.
The recirculated exhaust gas may need cooled prior to reentry into the intake system. The cooled gas reduces the oxygen content of the combustion mixture and reduces the temperature of the combustion mixture in the combustion chamber, decreasing the formation of NOx. Key components of an EGR system may include a turbocharger, an EGR cooler, and an EGR flow control valve. The turbocharger includes a compressor that is couples to and is driven by a turbine. The EGR cooler may be an air-air charge cooler. The EGR flow control valve regulates exhaust flow through the EGR circuit. An engine's electronic control module (ECM) may operate the EGR flow control valve.
While the EGR system provides a variety of advantages to operation of an internal combustion engine, it also requires energy for moving the exhaust gas and cooling the exhaust gas. Using waste heat to operate the EGR system could improve the efficiency of operation of an engine using an EGR system.